High Pressure - High Temperature methods

[bleu marine] Institut Néel High Pressure High Temperature Devices (max 8GPa, 1500°C)[/bleu marine]

Institut Néel also possesses two hydraulic presses for high pressure-high temperature (HP-HT) syntheses up to 8 GPa. (Instrumentation -MCMF Tech group). These are used to stabilize strongly distorted oxides as perovskites with multiferroic properties, and to search for new compounds by exploring phase diagrams of oxides with unusual valence states or coordination, leading to interesting physical/structural properties. SPMCE - MCMF group focuses on solid solutions between 3d metals on the B-site of Bi, Pb or rare-earth containing distorted perovskites. HP-HT chemistry is also applied to the preparation of new superconducting compounds as (Ba, K)Fe2As2.

[bleu marine] Studies of effect on powder BiCrO3 perovskite under High Pressure High Temperature.[/bleu marine]

Defect-hydride structures may be stabilized using high pressure hydrogenation which activates metal atoms diffusion. Subsequent heat treatment gives way to vacancy coalescence resulting in nanoporous materials. This technique of generating vacancies in a hydride phase and subsequent degassing provides a method to introduce pores in metals from which novel properties can be expected. Metallurgy is mainly developed at high pressures on new Mg-based ternary hydrides or for ordered metal-vacancy-systems but also powder metallurgy is performed at ambient pressure on low temperature hydrides, magnesium-based hydrides or magneto-caloric materials (IICE-MCMF). By reacting magnesium or magnesium hydride with the first row transition metals new ternary hydrides based on transition metal-hydrido complexes are synthesized. The parent corresponding binary alloys do not exist, whereas the new metal framework held together by hydrogen does exist. This opens up possibilities to reduce the stability with respect to desorption. We anticipate to produce such phases by the use of high H pressure.

[bleu marine] Crystallographic structure of Mg7TiH14[/bleu marine]

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